The preforms used in such a method and machine are traditionally produced by injecting a thermoplastic material, such as polyethylene terephthalate (PET), in an injection cavity. The produced preforms are then fed to the machine for producing containers, wherein each preform is first heated to a temperature greater than the vitreous transition temperature and lower than the crystallization temperature of the thermoplastic material of the preform and then is formed into a container by injecting an incompressible liquid inside the heated preform, the incompressible liquid filling the shaped container.
Such a method is known and allows obtaining in a continuous and reproducible manner and at a high rate, containers, for example bottles of any shape and content, which are robust and filled with liquid. The liquid injected in the containers is for example the end liquid provided to the user of the containers.
Document US 2011/135778 A1 describes a method for simultaneously forming and filling a plastic container.
However, in some cases, the containers are not properly shaped and are susceptible of bursting inside the molds in which they are produced. Indeed, the preforms are subjected to a rapid shift in temperature since the preforms have been heated and are filled with a liquid, which is generally at a temperature below the temperature of the preform. Such a change of temperature can lead to malformation of the containers if the cooling of the thermoplastic material of the containers is not homogenous. When such an event occurs, the liquid injected in the preform is spilled and soils the machine for producing the containers and the machine has to be stopped in order to be cleaned before production of containers can continue. Consequently, the bursting of a container greatly reduces the throughput of the machine since the machine is stopped during the cleaning operations.
One of the aims of the invention is to overcome this drawback by proposing a method and a machine for producing containers wherein the bursting of containers during the forming and filling step can be prevented.
Document US 2010/140280 describes a method for producing a bottle, where hoop stiffness and bottle geometry are used to control the bottle shape resulting from deformation caused by vacuum creation as water vapor permeates outwardly through the bottle walls.
Document DE 10 2012 102 357 describes a device comprising a control apparatus to control the device depending on the temperature of performs.
Document DE 10 2012 102 073 A1 describes a method for controlling preforms using at least a camera. Document WO 2014/075770 A1 describes a method for controlling the neck of a preform using a stereoscopic objective.
One of the aims of the invention is to offer different methods and machines for producing containers wherein the bursting of containers during the forming and filling step can be prevented.